(covers information from several alternate timelines)
The Krenim commandant attacked the USS Voyager aboard his patrol ship when it entered Zahl space. He hailed her and informed Captain Janeway that the territory Voyager was in was no longer Zahl, but was in dispute. He threatened to destroy Voyager if Janeway did not turn around but she ignored him and was informed by a Zahl official that she had nothing to worry about, that the Zahl defeated the Krenim years ago.
The Krenim commandant later returned and accused Janeway of assisting the Zahl and again threatened Voyager. Suddenly a temporal shock wave overtook the ships and the Krenim commandant's ship doubled in size and firepower, the Zahl vanished and the commandant fired on Voyager causing heavy damage and forcing Voyager to retreat. (VOY: "Year of Hell")
When the timeline was later negated, Voyager encountered the commandant when they entered Krenim space. The commandant informed them the region was in dispute and advised they avoid Krenim territory. Captain Janeway thanked him for the warning and Voyager altered course without incident. (VOY: "Year of Hell, Part II")
These four Krenim officers worked for Annorax on his weapon ship and operated controls inside the temporal chamber assisting in erasing species from the timeline. (VOY: "Year of Hell", "Year of Hell, Part II")
The Krenim scientist was assimilated by the Borg at some point prior to 2374. His (or her) personality was debating the finer points of temporal physics with Kathryn Janeway while manifested in Seven of Nine due to the vinculum. (VOY: "Infinite Regress")
Annorax's wife was one of the reasons Annorax was trying to change the timeline. He explained to Chakotay that the first time he used his weapon ship to eliminate the Krenim's enemy and restore the Krenim Imperium, he also killed fifty million Krenim, including his wife. He spent the next two hundred years trying to undo his mistake and restore his wife's life. After the Voyager crashed into his weapon ship, destroying it, time was restored, and Annorax was reunited with his wife. She came to his desk in their home on Kyana Prime and asked him to have breakfast with her and enjoy that beautiful day. Annorax first hesitated as he was close on his working goals but agreed and left with her. (VOY: "Year of Hell, Part II")